Population research at Johns Hopkins benefits greatly from the facilities provided by The Hopkins Population Center. Funds are requested to provide continuing support to five core units, and to provide support for the first time to a new core unit. Ongoing units include: Administrative Unit: supports general management of Center activities; promotes population research throughout the University; and collaborates in the presentation of five seminars series for Center Associates. Data Processing Unit: provides Center Associates with access to micro and mainframe computing facilities; maintains data archives for Associates; provides computer programmers. Information Unit: maintains a library, information retrieval services, and distribution of working papers and reprints for Center Associates. Mathematical/Statistical Services Unit: provides Center Associates with ready access to four highly skilled statisticians for advice on all aspects of population research. Electron Microscope Unit: maintains an electron microscope and supporting equipment. In the new grant period, we propose to add the following sixth core unit to further strengthen the facilities available in the area of reproductive biology. Radioimmunoassay Unit: provides the personnel, equipment and facilities required to perform radioimmunoassays. These six core units will provide services to 17 projects in demography/reproductive health and reproductive biology. A total of 30 University faculty members are affiliated with The Hopkins Population Center, as Center Associates, Center Staff, or members of Center Advisory Councils. The faculty represent 10 departments from 4 major University divisions (Public Health, Arts and Sciences, Medicine, and The Chesapeake Bay Institute). Population research at Hopkins in recent years, as evidenced by the list of publications submitted with this application, has made important contributions in both demography/reproductive health and reproductive biology. With the continued support of The Hopkins Population Center requested in this proposal, we expect to continue that record of productive research.